Light and electron microscopy showed the same distribution of glycogen. The peritoneal cells contain large amounts in all three body regions investigated: the forepart, metameric region and postannular region. Glycogen is present in most epidermal cells and is very abundant in some, particularly in the postannular region, but the cells which secrete the chitinous and proteinaceous components of the tube are almost devoid of glycogen.

A few studies on the excretion of organic matter by marine phytoplankton in culture have been reported (Guillard & Wangersky, 1958; Wangersky & Guillard, 1960; Stewart, 1963; Hellebust, 1965). Eppley & Sloan (1965) reported extensive excretion in Skeletonema costatum (Greville) Cleve cultures as they approached senescence and emphasized that excretion is inversely proportional to the physiological activity of cells. Hellebust (1965) demonstrated the release of high amounts (up to 38% of the carbon assimilated) of organic matter by Sk. costatum cells exposed to low light intensities. It is apparent that more knowledge is needed in order to define the intra- and extracellular factors affecting the excretion.

Among the marine invertebrates whose settlement behaviour is well studied, the polychaete tubeworm, Spirorbis spirorbis L. ( = borealis Daudin), the barnacle, Balanus balanoides, and the oyster, Ostrea edulis, are different in form whether in the free-swimming or adult stage, yet the settlement behaviour patterns are basically similar (Crisp, 1973). The larvae have a sequence of movements during exploration of the substratum, with each activity initiated by a hierarchy of stimuli. Given a positive set of responses to a suitable habitat, the distances moved on the substratum are limited progressively so that finally the larva investigates a very restrictred area. When the exact site for settlement is determined the larva ceases to move, attaches permanently and immediately commences metamorphosis into the adult form. However, if certain stimuli are lacking or obnoxious to the searching larva, it recommences the initial free-swimming activity, in order to reach alternative substrata.

It has been suggested in Part IV of these contributions that the larger diameter of centric diatom cells met with in collections made in the oceans in the lower latitudes might be caused in part by the relatively greater grazing known to take place in these areas (Steemann-Nielsen, 1962; Lohmann, 1912). Eight series of experiments were therefore carried out to determine any effect that might be attributed to animals grazing on populations of centric marine diatoms.

Frontal horns are prominent structures, characteristic of the nauplii of most cirripedes. Such horns are more prominent amongst the Lepadomorpha, i.e. Lepas (see Groom, 1894).

Reference is made to frontal horns in those papers concerned with the identification of nauplii (Nilsson-Cantell, 1921; Herz, 1933; Bassindale, 1936; Batham, 1946; Pyefinch, 1948; Buchholz, 1951; Barnes and Barnes, 1959a, b), but more detailed descriptions of horns and associated gland cells are limited to the studies of Groom (1894), Kaufmann (1965) and Walley (1969).

In the present study, the morphology of the frontal horns and the cytology of associated frontal horn gland cells of three barnacle species - Balanus hameri (Ascanius), Balanus balanoides (L.) and Elminius modestus Darwin were investigated.

Adult European flat oysters, Ostrea edulis L., receiving a food supplement of the unicellular alga Tetraselmis suecica (Kylin) Butch, during laboratory conditioning for spawning produced more broods of larvae than oysters receiving only the natural phytoplankton in the seawater supply. Many of the broods from adults receiving this extra food were liberated sooner, and these larvae grew at an enhanced rate and provided greater spat yields than the broods from the control stock. The viability of larvae, which was significantly correlated with their lipid, and in particular neutral lipid, proportion at the time of liberation, declined as the length of the stock-conditioning period prior to female spawnings increased. This may be related to the decline in the dry meat weight and the condition factor of the adult oysters during the experiments irrespective of the feeding regime. The extra algal ration provided a check to the decline in dry meat weight of the food-supplemented adults.

Recent equations for calculating the osmotic coefficient of sea water from the properties of the component single-electrolyte solutions are discussed. Two equations are introduced that together provide accurate predictions of the osmotic coefficient of sea water for ionic strengths up to 4 M (equivalent to a fivefold concentration of standard sea water). Since they take into account the detailed solution composition these equations should be useful for calculating the osmotic coefficients of estuarine waters and of biological salines where procedures based on curve fitting to standard sea-water data may be inapplicable. Extensions of the calculations to cover a wide pressure and temperature range are discussed in some detail.

In spite of the large number of Chlamydomonas species which have been described, there is very little information on those occurring in marine or brackish environments. Many of the earlier descriptions may be disregarded as being not sufficiently complete for recognition (e.g. Schiller, 1913, 19255 West, 1916; Wille, 1903), whilst in recent years only a few marine species have been observed and studied in detail (Chadefaud, 1951; Dangeard, 1965; Ettl, 1967).

A seasonal survey of particulate and dissolved organic material was made at E1 in the English Channel during 1968. The average integral mean values were: dissolved organic carbon 65 μg-at C/l (780 μg C/l); dissolved organic nitrogen 4·6 μg-at N/l (64 μg N/l); dissolved organic phosphorus 0·12 μg-at P/l (3·8 μg P/l); particulate organic carbon 190 μg C/l and particulate organic nitrogen 21 μg N/l. Dissolved organic carbon and the particulate organic carbon and nitrogen showed increases subsequent to the spring bloom; such increases were less evident in the dissolved organic nitrogen results and not apparent in those of dissolved organic phosphorus.

Analyses were also made in March and June in 1969 at two other stations in the English Channel, in addition to E1. The results from the three stations were basically similar.

Concentrations of copper, zinc, lead, manganese and iron in the brown seaweed Fucus vesiculosus have been measured in samples collected over its range of distribution in four estuaries having different degrees of metal contamination. Factors controlling the concentrations in the weed have been studied and include the concentrations of metals in the water, seasonal changes, the position of the weed in the intertidal zone and the particular portion of the plant which is analysed. It is concluded that analysis of the weed gives a reasonable indication of average conditions in the water at points along an estuary and provides a method of making comparisons with the same estuary in subsequent years or with other estuaries.

Trace metals have been determined in the sediments, waters and fauna of a sewagesludge disposal area in the Firth of Clyde. Enhanced values of organic carbon and several metals were found in the sediments of the immediate deposit area. The results are discussed in relation to local background variations and compared with data from the Solway Firth. Trace-metal concentrations in the waters of the deposit area were higher than those from further off shore in the Clyde.

Epifaunal species showed rather erratic variation in trace metal content, unrelated to total or readily extractable trace metals in the underlying sediment. The tracemetal content of demersal fish species was not significantly different from figures reported for elsewhere in the United Kingdom.

The distributions of some in-faunal and epifaunal species in the area are described.

It is concluded that the effects of sewage sludge disposal in this area are local, gross changes being limited to an area of about 20 km2 of sea-bed. However, little is known of the overall effects of toxic wastes particularly at threshold levels, and further monitoring is required.